Pressure differentiated exhaust aftertreatment device

ABSTRACT

The disclosure relates to an exhaust gas aftertreatment device for purification of exhaust gas emissions. The exhaust gas aftertreatment device is arranged in an exhaust gas passage subsequently of an internal combustion engine and includes an encapsulating portion, a first catalytic substrate and a second catalytic substrate. The second catalytic substrate may be of SCR type. The exhaust gas aftertreatment device includes a reductant injecting device, a pipe and an obstructing portion, where the reductant injecting device is arranged such that reductant is injectable within the pipe and the exhaust gas flow through the pipe can be controlled by the obstructing portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C.§119(a)-(d) to European patent application number EP 14174794.9, filedJun. 27, 2015, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to an exhaust gas aftertreatment devicefor an internal combustion engine. The disclosure can be applied inpassenger cars as well as in heavy duty vehicles such as trucks orbuses.

BACKGROUND

In order to fulfill current stringent emission legislation more or lessall vehicles with internal combustion engines are provided with anexhaust gas aftertreatment device comprising at least one catalyticconverter with at least one catalytic substrate. A catalytic convertersubstrate generally comprises a channeled structure which exhaust gasescan pass through while being exposed to the large surface area of thecatalytic substrate. The channels of the substrates may be fluidlyconnected by perforating holes or like allowing gases to pass betweenadjacent channels. This enables gas to diffuse through the substratestructure. For petrol engines the most frequently used catalyticconverters are of Three Way Catalyst (TWC) type, while catalyticconverters of Diesel Oxidation Catalyst (DOC) type and/or Lean NOx Trap(LNT) type are the most frequently used converters for diesel engines.The TWC or the DOC/LNT may be supplemented by a converter with SelectiveCatalytic Reduction (SCR) functionality for improved NOx reduction.Typically, when using a catalytic converter of SCR type a liquid orgaseous reductant is added to the exhaust gas emission flow before theexhaust gases enters the catalytic converter of SCR type. The additionof reductant enables the catalytic reduction were NOx is reduced todiatomic nitrogen, N2, and water, H2O.

Catalytic converters combining the functionalities of more than one typeof catalytic converter in one catalytic converter also exist.

Combining more than one catalytic converter can be problematic sinceexhaust gas aftertreatment devices often are associated with designrestrains due to the limited available space in the engine compartment.Thus, small exhaust gas aftertreatment devices are preferred from anengine packaging perspective, but small exhaust gas aftertreatmentdevices usually means that the flow distance between the inlet and thecatalytic substrates of the catalytic converter is limited. Limiteddistance means that the time and distance during which mixing of theexhaust gas emissions can occur is limited. Insufficient mixing of theexhaust gas emissions gives inhomogeneous exhaust gas emission mixture.This might e.g., be problematic for emission gas sensors, arranged inthe exhaust gas emission flow, to work properly and give accurateemission measurements.

Other problematic areas for catalytic converters are high back pressureand insufficient heating. High back pressure implies significant exhaustgas flow resistance. This is negative for the efficiency of thecombustion engine resulting in a decrease of power output. Compensationof such decrease in power output leads to an increase in fuelconsumption. If there is a difference in back pressure between twopossible flow paths the flow through the flow path with lowestbackpressure will be larger than the flow through the flow path with thehigher backpressure. The flow ratio will be in proportion to thedifference in back pressure. Heating of the catalytic converter iscrucial since the catalytic converter is most effective at relativelyhigh temperatures. Thus, it is desirable that the catalytic converterreaches its optimum operation temperatures as soon as possible and thatthe catalytic converter stays warm during operation.

Insufficient mixing of the exhaust gas emissions are of particularinterest if a catalytic converter with a catalytic substrate with SCRfunctionality is used. For catalytic converters with SCR functionality,a liquid or gaseous reductant such as e.g., urea is introduced in theexhaust gas emission flow in order for the reductant and exhaust gasemissions to mix before reaching the substrate with SCR functionality.When a liquid reductant is used it is also desirable that the liquidreductant is evaporated. Consequently, sufficient mixing and reductantevaporation is important for the substrate with SCR functionality towork properly.

U.S. Pat. No. 8,607,551 discloses an exhaust gas purifier and system forexhaust gas purification including an NOx catalyst of SCR type and aCatalyst Supported diesel particulate Filter (CSF) arranged in series,and being dispensed in an exhaust passage of an internal combustionengine. The purifier includes a passage for urea supply having ahydrolysis catalyst therein and a passage for hydrocarbon supply havingan oxidation catalyst therein. Prior art, described in FIG. 4, disclosesa DOC, a CSF and a catalyst of SCR type is arranged in series. A ureainjection valve is arranged in a pipe upstream of the catalyst of SCRtype. Neither in U.S. Pat. No. 8,607,551 nor prior art therein providessufficient mixing and reductant (urea) evaporation characteristics andrespective design are limited in regards of engine compartment packagingrequirements.

Thus, there is a need for further improvements.

SUMMARY

An object of the present disclosure is to provide a compact exhaust gasaftertreatment device, in particular a compact two catalytic converterexhaust gas aftertreatment device with improved catalytic properties dueto improved mixing and reductant evaporation characteristics. Byarranging two catalytic converters in series, wherein the secondcatalytic converter is of SCR type, and applying a pressure differentialin connection to the injection of reductant a compact exhaust gasaftertreatment device with desired shape and improved mixing andreductant evaporation characteristics is provided.

Further advantages and advantageous features of the present disclosureare disclosed in the following description and in the dependent claims.

Another object of the present disclosure is to provide a manufacturingmethod of such exhaust gas aftertreatment device.

As is known to a person skilled in the art a catalytic converter maycomprise more than one catalytic substrate. E.g., catalytic convertersof TWC type generally comprise two substrates. It is also possible touse a single catalytic substrate with coating providing two differentfunctionalities, such as the functionality of DOC type and of LNT type.This is not part of the present disclosure per se and for clarity andsimplicity reasons hereinafter the respective catalytic converter of thepresent disclosure is simply referred to as a first and a secondcatalytic substrate. With respective first and second catalyticsubstrate catalytic converters possibly comprising more than onesubstrate are considered to be included.

The present disclosure can be used both in vehicles with spark ignitedengines and in vehicles with compression ignited engines. If the exhaustgas aftertreatment device is used in a vehicle with a diesel engine thefirst catalytic substrate may be of Diesel DOC type or LNT type. If theexhaust gas aftertreatment device is used in a vehicle with a gasolineengine, or any other spark ignited fuels such as e.g., an ethanol basedfuel, the first catalytic substrate may be of TWC type. The technicalaspects of DOC, TWC and LNT catalyst are known to a person skilled inthe art, as is the advantages and disadvantages with respective type ofcatalyst. The type of catalytic converter used as first catalyticconverter is not part of the disclosure per se.

Thus, as will be apparent throughout the description of the presentdisclosure, when referring to said first catalytic substrate what mightbe intended is a catalytic converter of TWC type, thus actuallycomprising of two catalytic substrates.

Exhaust gas aftertreatment devices for purification of exhaust gasemissions for vehicles are generally arranged in exhaust gas passagessubsequently of an internal combustion engine. As the exhaust gasemissions of said internal combustion engine are discharged through saidexhaust gas passage they enter said exhaust gas aftertreatment device.The exhaust gas passage is generally enclosed by an encapsulatingportion enclosing of the exhaust gas aftertreatment device.

The exhaust gas aftertreatment device of the present disclosurecomprises said first catalytic substrate and said second catalyticsubstrate, wherein said first catalytic substrate is arranged upstreamof said second catalytic substrate. The first and second catalyticsubstrates are arranged such that respective catalytic substrate coversa majority of respective flow cross sectional area of said exhaust gaspassage. The whole cross sectional area of the catalytic converter maybe covered, but as will be apparent according to some embodiments of thepresent disclosure part of the cross sectional area may be occupied bye.g., a reductant injecting device or a reductant injecting pipe. Partof the cross sectional area may also be used in order to provide exhaustgas circulation.

The first and second catalytic substrates are extending a respectivelength in a flow direction of said exhaust gas passage such that anexhaust gas emission flow discharged from said internal combustionengine flows through the length of said first catalytic substrate andsubsequently through the length of said second catalytic substrate.

According to the present disclosure the second catalytic substrate maybe of Selective Catalytic Reduction (SCR) type. However, the secondcatalytic substrate may also be of other design where injection of aliquid or gaseous fluid with reductive, or other chemical property, isdesired.

Thus, according to the present disclosure the exhaust gas aftertreatmentdevice additionally comprises a reductant injecting device, capable ofinjecting liquid or gaseous reductant into the exhaust gasaftertreatment device. The reductant injecting device may comprise atleast an injector nozzle and an injector conduit arranged such that theinjector conduit extends through the encapsulating portion of theexhaust gas aftertreatment device. The injector nozzle, arranged to thepart of the reductant conduit extending into the exhaust gasaftertreatment device, is provided such that reductant can be added tothe exhaust gas flow. The reductant injecting device may be arranged toa reductant tank and to means suitable for providing reductant from thereductant tank to the reductant injecting device. The functionality ofan SCR catalyst and a reductant injecting device as disclosed above areconsidered to be known to a person skilled in the art and are not partof the present disclosure per se.

According to the present disclosure a pipe extends in said flowdirection of said first catalytic substrate such that said pipe providesa passage through said first catalytic substrate. Said pipe comprises anobstructing portion arranged such that said obstructing portion coversthe cross sectional area of said pipe. The obstructing portion isprovided such that a difference in back pressure is obtainable betweensaid pipe and said first catalytic substrate. The pressure differenceobtained provides different flow rates for the exhaust gas flow throughthe first catalytic substrate and for the exhaust gas flow through thepipe. Said reductant injecting device is extending through saidencapsulating portion and into said pipe such that reductant isinjectable within said pipe.

In order for a catalytic substrate of SCR type to efficiently purifyexhaust gases suitable relation between injected reductant and exhaustgases, sufficient evaporation of injected reductant and good mixing ofevaporated reductant and exhaust gases are required. The mixing andevaporation properties are favored by turbulent exhaust gas flow andmaintained high exhaust gas temperature. Also, the longer the time andthe distance during which the exhaust gas and the injected reductant canmix is the better mixing and reductant evaporation is obtained.

By arranging the reductant injecting device within said pipe thedistance from where the reductant is injected to the subsequentlyarranged catalyst of SCR type will be prolonged which will be beneficialfor mixing and reductant evaporation.

Thus, according to an embodiment of the present disclosure saidreductant injection device is arranged such that said reductant isinjectable downstream of said obstructing portion. As has been stated,injecting the reductant downstream of said obstructing portion, whereinsaid obstructing portion is arranged in a pipe, enables that reductantis injectable further away from the second catalytic converter thanotherwise would be possible.

According to one embodiment of the present disclosure said pipe isarranged centrally of said first catalytic substrate. Arranging the pipecentrally of said first catalytic substrate may be advantageous from amanufacturing perspective. However, it is also possible to arrange thepipe radially displaced. Depending on the design of the exhaust asaftertreatment device displacing the pipe radially may be used in orderto improve the mixing properties. Since the exhaust gas flow through thefirst catalytic substrate and the pipe will be different, by displacingthe pipe radially it is possible to obtain a swirling, turbulent flowmotion after the pipe and the first catalytic converter which isbeneficial for the mixing characteristics.

The obstructing portion may be of different configurations. According toone embodiment of the present disclosure said obstructing portion has ahigher back pressure than said first catalytic substrate. According toan embodiment of the present disclosure the difference in back pressurebetween the pipe, provided by the higher back pressure of theobstructing portion provided in the pipe, and the first catalyticsubstrate may be configured such that approximately 10% of the exhaustgas mass flow flows past the obstructing portion, not taking the smallercross sectional area of the obstructing portion in consideration.According to another embodiment as low as 2% of the mass flow flows pastthe obstructing portion. Depending on current exhaust gas aftertreatmentdevice design the obstructing portion may have anything from merelynoticeable gas flow obstructing effect to being completely impermeable.Applying a completely impermeable, or at least significantly flowreducing obstructing portion, may be an advantageous approach with highcontrollability of the mixing and evaporative characteristics within thepipe.

According to one embodiment of the present disclosure said exhaust gasflow enters said exhaust gas aftertreatment device in a first flowdirection and is discharged from said exhaust gas aftertreatment devicein a second flow direction. Arranging the exhaust gas aftertreatmentdevice such that the exhaust gases are discharged in a direction turnedapproximately 90° in relation to the direction in which the exhaustgases enters the exhaust gas aftertreatment device is beneficial from avehicle packaging perspectives.

According to another embodiment of the present disclosure said pipe iscircumferentially perforated by radial holes along at least a portion ofthe length of said pipe such that exhaust gas emission can flow throughprovided perforation. Depending on prevailing pressure ratio between theinside and outside of the pipe, the perforation of said pipe may enableexhaust gases to pass out of the pipe and to said first catalyticsubstrate or pass from the said first catalytic substrate into the pipe.As previously stated, the channels of a substrate may be fluidlyconnected such that exhaust gases passing through said perforation ofsaid pipe may continue to diffuse in the substrate structure.Perforation of said pipe, enabling that exhaust gas may pass in or outof said pipe, can be used to improve the mixing characteristics of theexhaust gas aftertreatment device. The radial holes may according toanother embodiment of the present disclosure continue through thesubstrate.

Different examples of how the arrangement of said obstructing portion,the arrangement of said reductant injecting device, perforation of saidpipe and the exhaust gas aftertreatment device design can be used inorder to obtain required mixing and reductant evaporationcharacteristics will be disclosed in the detailed description.

According to another embodiment of the present disclosure saidencapsulating portion comprises, in the order of the exhaust gas flow:

an inlet portion,

a first substrate outer encapsulating portion,

a turnaround surface portion,

a mixing area encapsulating portion,

a second substrate encapsulating portion, and

an outlet portion.

Thus, the exhaust gas flow discharged from the internal combustionengine initially enters said exhaust gas aftertreatment device at saidinlet portion in said first flow direction, where after the exhaustgases passes the first substrate outer encapsulating portion comprisingthe first catalytic substrate and enters the turnaround surface portion.Subsequently the exhaust gas flow passes the mixing area encapsulatingportion into the second substrate encapsulating portion comprising thesecond substrate. At said mixing area a homogeneous exhaust gas andevaporated reductant mix is obtained. Finally the purified exhaust gasis discharged from said exhaust gas aftertreatment device at said outletportion in said second flow direction. Said turnaround surface portionprovides a turnaround surface provided between said first catalyticsubstrate and said second catalytic substrate. At said turnaroundsurface the exhaust gas flow may be redirected in some direction inorder for the exhaust gas aftertreatment device to comply withprevailing packaging limitation, e.g., such that said exhaust gas flowis redirected from said first flow direction to said second flowdirection. Thus, such arrangement is advantageous from a packagingperspective, wherein said first flow direction may be perpendicular ornear perpendicular to said second flow direction whereby the exhaust gasaftertreatment device can be arranged in a 90° angled exhaust gaspassage.

Depending on the packaging requirements it is also possible that otherangulations of the exhaust gas aftertreatment device are mostadvantageous.

The positioning of the reductant tank may be adapted in order to complywith current engine design. Also the reductant injecting device may bearranged in order to comply with current engine design, and in order toprovide sufficient reductant injection pressure it may be advantageousto position the reductant tank and the reductant injecting device closeto each other.

Depending on the vehicle design and engine packaging requirements it maybe beneficial to position the reductant tank and the reductant injectingdevice either before said exhaust gas aftertreatment device, or at leastsuch that said reductant injecting device is extending through saidencapsulating portion upstream of said first catalytic substrate, orafter said exhaust gas aftertreatment device, or at least such that saidreductant injecting device is extending through said encapsulatingportion downstream of said first catalytic substrate.

Hence, according to one advantageous embodiment of the presentdisclosure said reductant injecting device is arranged such that itextends through said turnaround surface of said encapsulating portion ata position downstream of said first catalytic substrate. According toanother embodiment of the present disclosure said reductant injectingdevice is arranged such that is extends through said encapsulatingportion at said first substrate outer encapsulating portion at aposition downstream of said first catalytic substrate.

According to the embodiment of the present disclosure for which thereductant injecting device extends through said outer encapsulatingportion at a position downstream of said first catalytic substrate thereductant injecting device may additionally extend through saidobstructing portion. This enables that reductant is injectable withinsaid pipe downstream of said obstructing portion.

The reductant may be injected either substantially in said first flowdirection or in a flow direction substantially opposite to said firstflow direction.

Injection of reductant opposite the flow direction may be advantageousfor the mixing since the injected reductant will have more momentum.However, installation restraints may limit the injection to be performedin parallel to the flow direction. Thus, what injection direction thatis most suitable for respective embodiment of the present disclosure isdependent on current exhaust gas aftertreatment device design. Theinjection direction is one of the many disclosed properties that can beadapted such that sufficient mixing and evaporation characteristics areobtained.

According to another embodiment of the present disclosure saidturnaround surface is provided with a porous material. Implementing suchporous material may be beneficial due to many different causes. Thereductant is injected upstream of said porous material and consequentlyunevaporated reductant can be absorbed by the porous material andretained until it is fully evaporated. The porous material may consistof a mesh structure, such as for a catalytic converter substrate, or beof any other suitable structure. According to one embodiment of thepresent disclosure said porous material is made of a heat conductivematerial such that said porous material is usable as a heater element,which improves the ability to evaporate not evaporated reductant evenmore. According to one embodiment said porous material is provided witha catalytic surface.

The present disclosure also comprises a vehicle comprising the exhaustgas aftertreatment device of the present disclosure and methods formanufacturing said first catalytic substrate, comprising saidobstructing portion, of said present disclosure.

According to one embodiment of a method for manufacturing a catalyticsubstrate comprising said obstructing portion is manufactured by usingextrusion. Extrusion and cutting catalytic substrates generallycomprises the method steps of:

mixing a substrate material, wherein said substrate material is suitablefor forming a catalytic substrate structure,

extruding said substrate material through a die, wherein said die is ofa suitable shape such that a mesh structure, honeycomb structure orother desired structure is formed,

removing liquid from said extruded substrate material by suitable meanssuch as by drying said extruded substrate material by applying heat,

cutting said extruded substrate material such that a substrate ofsuitable length is formed,

performing heat treatment of said cut substrate in an oven or like suchthat said cut substrate gets hard and brittle, and

applying a catalytic coating to said cut substrate, wherein saidcatalytic coating is applied by suction, spraying or by dipping saidsubstrate in said catalytic coating.

Said catalytic coating comprises base metals and noble metals and havecatalytic and surface enlarging properties.

Extrusion of catalytic substrates according to the method steps asdescribed above are well known and are not part of the disclosure perse. The method steps can also be performed in a somewhat differentmanner with the same result.

However, according to the disclosure the method additionally comprisesthe steps of:

drilling a hole in parallel with an intended flow direction of saidcatalytic substrate such that the hole extends through said catalyticsubstrate,

arranging a pipe within said drill hole, and

arranging an obstructing portion within said pipe such that saidobstructing portion covers the cross sectional area of said pipe suchthat a difference in back pressure is obtainable between said pipe andsaid first catalytic substrate.

The latter method may also be performed without arranging a pipe withinsaid drill hole. Inserting a pipe is optional since the drilling itselfwill form a channel in the substrate. However, a pipe may be heated bythe hot exhaust gases, thus inserting a pipe may be advantageous from areductant evaporation embodiment.

According to an embodiment of the present disclosure said drill hole isarranged substantially centrally in said catalytic substrate. Thismanufacturing method of said first catalytic substrate comprises anobstructing portion if ceramic substrates are used. Extrusion of ceramicsubstrates is well known and by selecting suitable obstructing portionand pipe, and drilling a hole in said ceramic substrate suitable forsaid pipe, a first catalytic substrate of the present disclosure caneasily be obtained.

According to another embodiment of a method for manufacturing acatalytic substrate comprising said obstructing portion the methodcomprises the step of:

extruding a substrate with two different densities such that an innerportion in an intended flow direction, running from an intended flowentering side to an intended flow exiting side, of the extrudedsubstrate is more dense than an outer portion in an intended flowdirection, also running from an intended flow entering side to anintended flow exiting side, of the extruded substrate, such that saidinner portion is provided with an higher back pressure than said outerportion, and

drilling a hole in said inner portion, such that said inner portionforms an obstructing portion extending at least a part of the length ofsaid catalytic substrate, in parallel with an intended flow direction ofsaid catalytic substrate.

Such extrusion may be performed simultaneously as a pipe, separatingsaid two substrate portions with different substrate density, isarranged inside said extruded substrate.

In this manufacturing method of said first catalytic substrate thedenser portion of the extruded substrate forms an obstructing portionand the less dense portion of the extruded substrate forms a portionwhich may be provided with a catalytic coating.

According to one embodiment of a method for manufacturing a catalyticsubstrate comprising said obstructing portion the method comprises thestep of:

welding an obstructing portion within a ring shaped catalytic substratesuch that said obstructing portion seals against an inner peripheralsurface of said ring shaped catalytic substrate.

This manufacturing method of said first catalytic substrate comprises anobstructing portion of the present disclosure if metallic substrates areused. Metallic ring catalysts are commercially available and by weldinga suitable obstructing portion within such ring catalyst a firstcatalytic substrate of the present disclosure can easily be obtained.

As is apparent for the person skilled in the, as long as notcontradicting different embodiments presented can be combined withoutdeparting from the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments of embodiments herein, including its particularfeatures and advantages, will be readily understood from the followingdetailed description and the attached drawings.

FIG. 1 discloses a first embodiment of an exhaust gas aftertreatmentdevice according to the present disclosure;

FIGS. 2A and 2B disclose the second embodiment of an exhaust gasaftertreatment device according to the present disclosure where flow ofexhaust gas is indicated;

FIGS. 3A and 3B disclose different embodiments of exhaust gasaftertreatment devices according to the present disclosure;

FIG. 4 discloses a third embodiment of an exhaust gas aftertreatmentdevice according to the present disclosure; and

FIG. 5 discloses a fourth embodiment of an exhaust gas aftertreatmentdevice according to the present disclosure.

DETAILED DESCRIPTION

As required, detailed embodiments are disclosed herein. However, it isto be understood that the disclosed embodiments are merely exemplary andthat various and alternative forms may be employed. The figures are notnecessarily to scale. Some features may be exaggerated or minimized toshow details of particular components. Therefore, specific structuraland functional details disclosed herein are not to be interpreted aslimiting, but merely as a representative basis for teaching one skilledin the art.

FIG. 1 discloses a first embodiment of an exhaust gas aftertreatmentdevice 10 a, comprising a first catalytic substrate 30 of DOC type and asecond catalytic substrate 40 of SCR type. Centrally of said firstcatalytic substrate 30 a pipe 60 is arranged, and in the upstream partof the said pipe 60 an obstructing portion 70 is arranged. The exhaustgas aftertreatment device 10 a is encapsulated by an encapsulatingportion 20 a, wherein a reductant injecting device 50 a are extendingthrough said encapsulating portion 20 a at a part of the encapsulatingportion 20 a provided upstream of said first catalytic substrate 30.Said reductant injecting device 50 a also extends trough saidobstructing portion 70 such that reductant is injectable inside saidpipe 60 and downstream of said obstructing portion 70.

By introducing said pipe 60, and injecting the reductant within saidpipe 60 instead of injecting the reductant at a position provideddownstream of said first catalytic substrate 30, the distance from wherethe reductant is injected to said second catalytic substrate 40 will beprolonged. This means that the injected reductant will also be exposedto hot exhaust gases for a longer period of time before reaching thesecond catalytic substrate 40 of SCR type which will improve theevaporation properties of said reductant and also that injectedreductant and exhaust gases will be able to mix during a longer periodof time. A homogenous, balanced mix between exhaust gases and fullyevaporated reductant is desirable to obtain the best possible catalyticeffect by a catalyst of SCR type.

The obstructing portion 70 has a higher backpressure than said firstcatalytic substrate 30. In order for the first catalytic substrate 30 tobe efficient it is desirable that the exhaust gases spends as long timeas possible within the substrate and thereby is exposed to as largecatalytic surface as possible during the passage of the substrate. It isalso desirable that that the backpressure of said first catalyticsubstrate 30 is as low as possible since the engine efficiency isdependent on the gas flow through the exhaust system. Thus, there istrade-off between catalytic efficiency and backpressure of the firstcatalytic substrate.

In order for injected reductant and exhaust gases to mix sufficiently,and for the reductant to be sufficiently evaporated, the exhaust gasflow and the reductant injection rate has to be considered together. Byadding the obstructing portion 70, for which the backpressure is setindependently of having to consider catalytic efficiency, it is possibleto configure the backpressure, hence the exhaust gas flow, such that thegas flow through the obstructing portion 70 and the reductant injectionrate provides sufficient mixing and evaporation.

FIG. 2A shows an embodiment of the exhaust gas aftertreatment device 10b, comprising an encapsulating portion 20 b, a first catalytic substrate30 and a second catalytic substrate 40. Said encapsulating portion 20 bis divided in an inlet portion 100, a first substrate outerencapsulating portion 110, a turnaround surface portion 120, a mixingarea encapsulating portion 130, a second substrate encapsulating portion140 and an outlet portion 150. Said exhaust gas aftertreatment device 10b is intended to be provided in an exhaust passage downstream of aninternal combustion engine such that exhaust gases discharged from saidinternal combustion engine enters the exhaust gas aftertreatment device10 b at an inlet portion 100. The exhaust gases enters said exhaust gasaftertreatment device in a first flow direction A. After passing saidinlet portion 100 the exhaust gases passes the subsequently arrangedfirst catalytic substrate 30 comprising the pipe 60 with the obstructingportion 70 as described in connection to FIG. 1. On the outside of saidfirst catalytic substrate 30, which is covered by a first substrateinner encapsulating portion 170 which may be made of a metallicmaterial, an exhaust gas circulating space 160 is provided. Said exhaustgas circulating space 160 is in turn delimited by said first substrateouter encapsulating portion 110.

The exhaust gases passes said first catalytic substrate 30, said pipe 60and said obstructing portion 70 in the first flow direction A.Thereafter the exhaust gases reach said turnaround surface portion 120,provided such that a turnaround surface 200 is formed whereby theexhaust gas flow is redirected. Said turnaround surface is provided suchthat the exhaust gas flow will be redirected from said first flowdirection A in a redirecting movement C1-C2 to a first circulating flowdirection C1.

Said obstructing portion is arranged in the upstream part of said pipe60 such that a reductant injecting device 50 b is provided. Saidreductant injecting device 50 b is provided such that reductant isinjectable within said pipe 60 downstream of said obstructing portion70. Said reductant injecting device 50 b is extending through saidturnaround surface 200, substantially opposite the first flow directionA. Additionally, said reductant injecting device 50 b is provided suchthat reductant is injected in a direction substantially opposite to saidfirst flow direction A. By providing said reductant injecting device 50b inside said pipe 60 downstream of said obstructing portion 70 it ispossible to inject reductant further upstream from the second catalyticsubstrate 40, which is beneficial for the mixing and reductantevaporation characteristics.

Said turnaround surface 200 is additionally provided with a porousmaterial 220 a. Providing said porous material 220 a downstream of saidreductant injecting device 50 b enables that unevaporated reductant iscaptured and retained in said porous material 220 a. While retained insaid porous material 220 a the unevaporated reductant will be exposed tohot exhaust gases until fully evaporated. Said porous material 220 a canalso be configured in order to protect said turnaround surface fromcorrosion by preventing unevaporated reductant from reaching saidturnaround surface 200.

According to the embodiment of the disclosure disclosed in FIG. 2 abetween said turnaround surface portion 120 and said mixing areaencapsulating portion 130 a guiding means 210 is provided. Said guidingmeans may at least partly seal against the downstream edge of the firstsubstrate inner encapsulating portion 170 of said first catalyticsubstrate 30 and against the encapsulating portion 20 b.Circumferentially said guiding means 210 covers a section of thecircumference of said first catalytic surface such that a circulatingpassage 180 is formed where the redirected exhaust gas flow cancirculate in said redirecting movement C1-C2. Said guiding means 210provides that the at least a part of the exhaust flow is redirected andcirculated in said redirecting movement C1-C2.

Referring now to FIG. 2B, showing a cross sectional view of theembodiment of the exhaust gas aftertreatment device 10b shown in FIG.2A. The redirected exhaust gases enters the exhaust gas circulatingspace 160 in said circulating first flow direction C1, wherein saidexhaust gas circulating space 160 is provided such that said exhaustgases pursues said redirecting movement C1-C2 in a second circulatingdirection C2. Thus, the exhaust gas flow will pass on the outside ofsaid first catalytic substrate 30 when circulating in the secondcirculating direction C2.

Exhaust gas aftertreatment devices, and associated components, generallyhave a relative high temperature since being continuously exposed to hotexhaust gases. Catalytic converters generally works more efficiently athigher temperatures, thus maintained high temperature is beneficial forthe emission purifying effect of the catalytic substrate. However, sincethe exhaust gas aftertreatment device has a higher temperature than thesurroundings the outside of the exhaust gas aftertreatment devices 10 b,thus the encapsulating portion 20 b, is continuously cooled.

By directing hot exhaust gases in said redirecting movement C1-C2 insaid exhaust gas circulating space 160 the first catalytic substrate 30is not in direct contact with the first substrate outer encapsulatingportion 110. Instead flowing hot exhaust gases will separate the firstsubstrate outer encapsulating portion 110 from the first catalyticsubstrate 30. The temperature of the flowing hot exhaust gases, flowingpast said first substrate outer encapsulating portion 110, is lowereddue to the heat exchange with the surroundings. The first catalyticsubstrate 30 is continuously heated by hot exhaust gases passing throughsaid first catalytic substrate 30, and to some extent also heated by theexhaust gases passing the first catalytic substrate 30 on the outside.

After passing the outside of the first catalytic substrate in saidredirecting movement C1-C2 the exhaust gases subsequently enters saidmixing area encapsulating portion 130. At said mixing area encapsulatingportion 130 additional mixing of the exhaust gases are provided suchthat the a homogenous exhaust gas mix is provided before reaching saidsecond substrate encapsulating portion 140 where the second catalyticsubstrate 40 is provided. A homogenous exhaust gas mix is beneficial forthe catalytic conversion properties of the second catalytic substrate40. The exhaust gases subsequently flow through said second catalyticsubstrate 40 and to said outlet portion 150 in a second flow directionB.

FIGS. 3A and 3B disclose two different embodiments of exhaust gasaftertreatment devices 10 c; 10 d according to the present disclosure.The embodiment of the exhaust gas aftertreatment device 10 c of FIG. 3Ais similar to the embodiment of the exhaust gas aftertreatment device ofFIG. 2A with a few exceptions.

The embodiments of the disclosure disclosed in FIG. 3A disclose that thereductant injecting device 50 a is provided such that it extends throughsaid encapsulating portion 20 c upstream of said first catalyticsubstrate 30 and further through said obstructing portion 70, such thatreductant is injectable within the pipe 60. Additionally, said pipe 60is provided with perforations such that a perforated section 300 of saidpipe 60 is formed. Said perforated section 300 enables exhaust gases topass through a lateral surface of said pipe 60. Depending on thepressure difference and respective exhaust gas flow of the pipe 60 andof said first catalytic substrate 30 exhaust gases either pass saidlateral surface from said first catalytic substrate 30 into said pipe 60or from said pipe 60 into said first catalytic substrate 30. Dependingon current exhaust gas aftertreatment device design such perforatedsection 300 can be used for improved exhaust gas and reductant mixing.

The embodiment of the exhaust gas aftertreatment device 10 d of FIG. 3Bis similar to the embodiment of the exhaust gas aftertreatment device ofFIG. 3A with the difference that for the embodiment of the exhaust gasaftertreatment device 10 d of FIG. 3B a completely impermeable portion80 is provided in the upstream end of the pipe 60 and the obstructingportion 70 is provided in the downstream part of said pipe 60. Thereductant injecting device 50 c is provided such that it extends throughthe encapsulating portion 20 c upstream of the first catalytic substrate30 and through said impermeable portion 80 such that reductant isinjectable within said pipe 60 downstream of said impermeable portion 80but upstream of said obstructing portion 70. Additionally a section ofthe pipe 60 of the exhaust gas aftertreatment device 10 d of FIG. 3B isprovided with perforations such that a perforated section 300 is formed.

The embodiment of the present disclosure disclosed in FIG. 3B comprisesboth an obstructing portion 70 and an impermeable portion 80. Saidimpermeable portion 80 provides that all exhaust gases entering theexhaust gas aftertreatment device 10 d passes at least a portion of thefirst catalytic substrate 30. According to one embodiment of the presentdisclosure disclosed in FIG. 3B the obstructing portion 70 is configuredsuch that the backpressure of said obstructing portion 70 is lower thanthe backpressure of said first catalytic substrate 30. This will providethat exhaust gases will flow from the first catalytic substrate 30,through said perforated section 300 and into said pipe 60.

By controlling the backpressure of said obstructing portion 70 inrelation to the backpressure of said first catalytic substrate 30 it ispossible to control the flow of exhaust gases through said pipe 60 andsaid first catalytic substrate 30 respectively in order to optimizecatalytic conversion, mixing and evaporation characteristics.

It is also possible to use an obstructing portion, which is notcompletely impermeable, in the upstream part of the pipe such that thepipe comprises two obstructing portions, one provided in an upstreampart of said pipe and one provided in an downstream part of said pipe.For such embodiments of the present disclosure the reductant injectingdevice may be provided such that reductant is injectable between saidobstructing portions such that the backpressure of respectiveobstructing portion can be used to control the exhaust gas flow andmixing characteristics of said pipe.

Referring now to FIG. 4, disclosing an embodiment of the presentdisclosure. According to this embodiment of the exhaust gasaftertreatment device 10 e the exhaust gas flow enters said exhaust gasaftertreatment device 10 e in the first flow direction A. Said firstcatalytic substrate 30 is provided within the first substrate outerencapsulating portion 110 such that said first catalytic substrate 30seals against the encapsulating portion 20 d. Thus, for such embodimentof the present disclosure no exhaust gas circulating space 160 as ofFIGS. 2-3 is provided. After passing said first catalytic substrate or,as will be discussed more in detail later on, the obstructing portion70, the exhaust gas flow reaches the turnaround surface 200, wherein atsaid turnaround surface 200 the exhaust gas flow is redirected in thesecond flow direction B. The mixing area encapsulating portion 130 ofthe embodiment of the present disclosure disclosed in FIG. 4 is providedsuch that it extends substantially perpendicular to the first flowdirection A. The exemplary design of the exhaust gas aftertreatmentdevice 10e disclosed in FIG. 4 is beneficial from a packagingperspective for some vehicle designs.

Downstream of said mixing area encapsulating portion 130 the secondsubstrate encapsulating portion 140 is provided, wherein said mixingarea encapsulating portion 130 is narrower than said second substrateencapsulating portion 140. Such arrangement can be used to improve themixing characteristics of the exhaust gases before reaching the secondcatalytic substrate 40. A homogenous mix of exhaust gas and evaporatedreductant is beneficial for the catalytic conversion properties of thesecond catalytic converter 40 of SCR type. Downstream of said secondsubstrate encapsulating portion 140 is the outlet portion 150 arranged,wherein said outlet portion also is narrower than said second substrateencapsulating portion 140.

The reductant injecting device 50 d of the embodiment of the presentdisclosure disclosed in FIG. 4 is provided such that it extends throughthe encapsulating portion 20, upstream of the first catalytic substrate30, and into a reductant injecting pipe 90. Said reductant injectingpipe 90 is provided such that it seals against the encapsulating portion20 d and against the upstream edge of the pipe 60. Said reductantinjecting device 50 d is provided such that reductant is injectablewithin said reductant pipe 90 in a direction substantially parallel tosaid reductant pipe 90. Said pipe 60 is provided with an obstructingportion 70, wherein said obstructing portion is provided in thedownstream part of said pipe, and a perforated section 300. Inaccordance to what was discussed in connection to the embodiment of thepresent disclosure disclosed in FIG. 3B; by controlling the backpressureof the obstructing portion 70 in relation to the backpressure of thefirst catalytic substrate 30, it is possible to control the flow ofexhaust gases passing from the first catalytic substrate 30, trough saidperforated section 300, and into said pipe 60.

FIG. 5 discloses another embodiment of an exhaust gas aftertreatmentdevice 10 f of the present disclosure comprising a pipe 60 and anobstructing portion 70, wherein said obstructing portion is arranged inthe upstream part of said pipe 60. The embodiment of the presentdisclosure shown in FIG. 5 is provided in order to disclose analternative embodiment of a porous material 220 b and an alternativeembodiment of a reductant injecting device 50 e. The arrangement ofporous material, reductant injecting device, mixing area/encapsulatingportion/second substrate encapsulating portion 130, 140, 150 can be usedin order to tune the mixing and reductant evaporation characteristics ofexhaust gas aftertreatment devices according to the present disclosure.

Said reductant injecting device 50 e is provided such that it extendsthrough the turnaround surface 200 and into said pipe 60, such thatreductant is injectable within said pipe 60 at a position downstreamsaid obstructing portion 70. Further, the injection nozzle of saidreductant obstructing device 50 e is provided such that reductant isinjectable substantially in the first flow direction A. Said porousmaterial 220 b of the embodiment of the exhaust gas aftertreatmentdevice 10 f disclosed in FIG. 5 is provided at a distance from saidturnaround surface 200 such that an open space is provided between saidturnaround surface and said porous material 22 b.

The mixing area/encapsulating portion/second substrate encapsulatingportion 130, 140, 150 of the embodiment of the disclosure disclosed inFIG. 5 is arranged according to the arrangement disclosed in FIG. 4.

Depending on current design of the exhaust gas aftertreatment devicearranging said porous material 220 b, said reductant injecting device 50e and said mixing area/encapsulating portion/second substrateencapsulating portion 130, 140, 150 according to the embodiment of thepresent disclosure shown in FIG. 5 may be beneficial.

It is to be understood that the present disclosure is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the disclosure. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the disclosure.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the disclosure.

What is claimed is:
 1. An exhaust gas aftertreatment device forpurification of exhaust gas emissions, the exhaust gas aftertreatmentdevice for arrangement in an exhaust gas passage subsequently of aninternal combustion engine, and for enclosure by an encapsulatingportion of the exhaust gas passage, the exhaust gas aftertreatmentdevice comprising: a first catalytic substrate and a second catalyticsubstrate, the first catalytic substrate for arrangement upstream of thesecond catalytic substrate, the first and second catalytic substratesfor arrangement such that a respective catalytic substrate covers amajority of a respective flow cross sectional area of the exhaust gaspassage, and the first and second catalytic substrates for arrangementto extend a respective length in a flow direction of the exhaust gaspassage; a reductant injecting device; and a pipe for arrangement in theflow direction of the first catalytic substrate such that the pipeprovides a passage through the first catalytic substrate, the pipecomprising an obstructing portion for arrangement such that theobstructing portion covers a cross sectional area of the pipe such thata difference in back pressure is obtainable between the pipe and thefirst catalytic substrate; wherein the reductant injecting device isconfigured to extend through the encapsulating portion and into thepipe, such that reductant is injectable within the pipe.
 2. An exhaustgas aftertreatment device according to claim 1 wherein the obstructingportion has a higher back pressure than the first catalytic substrate.3. An exhaust gas aftertreatment device according to claim 1 wherein thereductant injection device is configured such that the reductant isinjectable downstream of the obstructing portion.
 4. An exhaust gasaftertreatment device according to claim 1 wherein the exhaust gas flowenters the exhaust gas aftertreatment device in a first flow direction(A) and is discharged from the exhaust gas aftertreatment device in asecond flow direction (B), and the reductant injecting device isconfigured such that the reductant is injectable substantially in thefirst flow direction.
 5. An exhaust gas aftertreatment device accordingto claim 1 wherein the reductant injecting device is configured toextend through the encapsulating portion upstream of the first catalyticsubstrate, and through the obstructing portion and into the pipe, suchthat reductant is injectable within the pipe and downstream of theobstructing portion.
 6. An exhaust gas aftertreatment device accordingto any of claim 4 wherein the reductant injecting device is configuredsuch that that the reductant is injectable within the pipe downstream ofthe obstructing portion, and such that the reductant is injectable in aflow direction substantially opposite to the first flow direction.
 7. Anexhaust gas aftertreatment device according to claim 1 wherein the pipeis circumferentially perforated along at least a portion of the lengthof the pipe such that exhaust gas emission can flow through providedperforation.
 8. An exhaust gas aftertreatment device according to claim4 wherein the encapsulating portion comprises, in the order of theexhaust gas flow: an inlet portion; a first substrate outerencapsulating portion; a turnaround surface portion; a mixing areaencapsulating portion; a second substrate encapsulating portion; and anoutlet portion; wherein the exhaust gas flow enters the exhaust gasaftertreatment device at the inlet portion in the first flow directionand is discharged from the exhaust gas aftertreatment device at theoutlet portion in the second flow direction, and wherein the turnaroundsurface portion provides a turnaround surface between the firstcatalytic substrate and the second catalytic substrate such that theexhaust gas flow is redirected from the first flow direction to thesecond flow direction.
 9. A vehicle comprising the exhaust gasaftertreatment device according to claim
 1. 10. A method formanufacturing a catalytic substrate comprising the obstructing portionaccording to claim 1, the method comprising: extruding and cutting acatalytic substrate; drilling a hole in parallel with an intended flowdirection of the catalytic substrate such that the hole extends throughthe catalytic substrate; arranging a pipe within the hole; and arrangingan obstructing portion within the pipe such that the obstructing portioncovers the cross sectional area of the pipe such that a difference inback pressure is obtainable between the pipe and the first catalyticsubstrate.
 11. A method for manufacturing a catalytic substratecomprising the obstructing portion according to claim 1, the methodcomprising: extruding a substrate with two different densities such thatan inner portion in an intended flow direction, running from an intendedflow entering side to an intended flow exiting side, of the extrudedsubstrate is more dense than an outer portion in an intended flowdirection, also running from an intended flow entering side to anintended flow exiting side, of the extruded substrate, such that theinner portion is provided with an higher back pressure than the outerportion; and drilling out a portion of the inner portion, such that theinner portion forms an obstructing portion extending at least a part ofthe length of the catalytic substrate, in parallel with an intended flowdirection of the catalytic substrate.
 12. A method for manufacturing acatalytic substrate comprising the obstructing portion according toclaim 1, the method comprising welding an obstructing portion within aring shaped catalytic substrate such that the obstructing portion sealsagainst an inner peripheral surface of the ring shaped catalyticsubstrate.